A hot blast method and a heat radiation method are two current methods of roasting coffee. The hot blast method is easily utilized in coffee roasters such as shown in U.S. Pat. Nos. 4,325,191 and 4,271,603. However, the hot blast method produces coffee which is sour and does not smell, or taste, like real coffee. On the other hand, while the heat radiation method maintains the smell and flavor of coffee, the construction of the roaster for the heat radiation method is complicated. Additionally, the heat radiation method takes a long time to roast the coffee.
Small size coffee roasters normally use a rotating roasting drum system, with the drum disposed in a housing. Therefore, as shown in FIG. 1, a drum 1 is formed of wire cloth and has an open end covered by a glass plate 2. Drum 1 is rotated by a motor 3. Coffee beans in drum 1 are heated by heater 4 disposed along an outer peripheral portion of drum 1. Alternatively, a drum 1 may be formed of heat resistant glass with wire cloth along its inner surface, as shown in FIG. 2. In these coffee roaster structures, the radiation heat from the heater element cannot be used effectively because the heater is disposed outside the roasting drum so that heat radiates without contributing to the roasting. To solve this disadvantage, the drum and heater can be sealed within the same container. However, the outer configuration of the roaster is increased and the heat efficiency is only somewhat improved.
There are also two types of process for roasting coffee, a continuous roasting process, and a non-continuous roasting process. In the continuous roasting process, the roasting process from roasting to cooling occurs within a single space or area. In this process, the time for the roasting process is relatively long because changing the appropriate temperature from the roasting process to the cooling process takes a long time. During this time, the smell and flavor of the coffee fails.
In the non-continuous roasting process, the roasting portion and cooling portion of the overall process are performed separately, in different areas or portions of the apparatus so that the above-mentioned disadvantage is eliminated. However, the shifting of roasted coffee beans from the roasting device to the cooling portion is generally carried out by hand. Thus, the efficiency and convenience of the roasting process is poor. Also, the cooling process must cool not only the roasted coffee beans, but also the interior of the roasting device so that the roasting process can be repeated soon after one roasting process has finished, since unroasted coffee beans cannot be placed directly in a hot roasting device. Therefore, such roasters are generally provided with two air circulating devices, one to cool down the roasted coffee beans in a cooling bin and the other to cool down the roasting device itself. The cost and size of such roasters thus increases.